[postgis-devel] GeoJSON Precision

[Darafei "Komяpa" Praliaskouski]

аў, 7 мая 2019, 4:17 PM карыстальнік Paul Ramsey <pramsey at cleverelephant.ca>
напісаў:

> This blog post reminded me:
>
>
> https://rapidlasso.com/2019/05/06/how-many-decimal-digits-for-storing-longitude-latitude/
>
> GeoJSON generation uses DBL_DIG as the number of decimal places, which is…
> a lot? 15 or 16 depending on your platform. I wonder if maybe we should
> crank that down to 8 as the default and let people crank it *up* as desired
> rather than emitting nanometer precision and expecting people to crank it
> *down* (they don’t).
>
> Thoughts?
>


There are number serialization libraries that choose number of digits
adaptively.

We had issues with 6 decimal digits serialization - vector roads visibly
don't match their rendered versions, so at least 7 would be my vote. I
believe 8 is safe, as it aligns with something called SQLMM_EPSILON of 1e-8
in the code.




> P
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